ab s t r ac t For many decades, the concentration polarization (CP) of uni-univalent salts arising within stagnant fluid films adjacent to charged surfaces in the presence of an electric field has been described by a simplistic model, designated here as classical theory. Barry [1] demonstrated that for a uni-univalent electrolyte the CP equation obtained by the aforementioned theory could also be derived from the Nernst-Planck equations. Here, as an extension of Barry's work, we deduce a CP

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... tion based on the Nernst-Planck equations applicable to steady transport of valence-asymmetric salts (salts containing ions of distinct valences, e.g., Na 2 SO 4 , CaCl 2 , FeCl 3 ) within stagnant fluid films in the vicinity of charged surfaces and in the presence of an electric field. It is shown that the expression derived matches the classical CP equation for similar conditions, despite some deceptive hypothesis assumed by the latter.